Many people are confused about what exactly
TrackBack
is and how you use it.
Here's a little explanation with pictures to help you understand.

So let's say I'm surfing the web and I'm reading my good friend Martin's
site.
I think it's funny, so I decide I want to post a link on my weblog about
it.

I click the permanent link so I can grab the URL for the entry.
I highlight it and copy it into the clipboard.

I go into my weblog tool (I happen to use
Movable Type),
and type my entry and paste
in the URL from Martin's site.

Now here's where the TrackBack thing comes in. Pay close
attention.

I want Martin to know I am talking about his post on my weblog.
This is the goal of TrackBack.

I go back to his weblog and link on the TrackBack text.

A new window pops up.
The first thing I'm told is the TrackBack URL.
The TrackBack URL is different than the regular URL for the entry.
You need to copy this URL.
If you don't use this URL, things will be all fuxxored and you will be
unhappy.

I paste the TrackBack URL into my weblog entry in the specific space
called URLs to Ping.
The TrackBack URL is the only thing that works here.

After previewing my entry and finally saving/publishing it,
I see the pings going out.

See the ping going to chokersandwich?
That's my site telling Martin's site that I'm talking about him.

When I go back to Martin's site, you see the change.
It now says TrackBack(1) instead of (0).

If I click on TrackBack(1) now, this window pops up.

See how this let's Martin and other readers know that I am talking about
this post on my weblog.

So, to review:

1) The purpose of TrackBack is to let a site know that you are
referencing
them on your on site.
2) The TrackBack URL is different than the regular permanent link URL.
3) TrackBacks are fun. You should use them.